1. Field of the Invention
The present invention relates to a multi-carrier communication system, and more specifically, to an apparatus for tracking a sampling clock of a multi-carrier communication system.
2. Description of the Prior Art
A transmitter of a multi-carrier communication system utilizes a plurality of sub-carriers to modulate predetermined transmitted data and transmits the modulated data to a receiver in the form of a continuous data flow. At this time, the receiver samples the above-mentioned continuous data flow utilizing a sampling clock. When the frequency of the sampling clock includes a small offset, a phase-shift may be occurred between the received symbol generated by the receiver and the original transmitted data transmitted by the transmitter. Therefore, the multi-carrier communication system compensates the above-mentioned N received symbols by estimating a sampling clock offset utilizing a plurality of pilot symbols to eliminate the effect caused by the sampling clock offset, wherein each pilot symbol is utilized for transmitting a predetermined data X. The receiver computes the sampling clock offset according to the received symbol R corresponding to the pilot symbol and the predetermined data X. Please refer to the following equation for the relationship between the received symbol R and the predetermined data X.
                              R                      i            ,            j            ,            k                          =                                            ⅇ                                                -                  j2                                ⁢                                                                  ⁢                π                ⁢                                  k                  N                                ⁢                                  τ                                      i                    ,                    j                                                                        ·                          ⅇ                              jψ                                  i                  ,                  j                                                      ·                          H                              j                ,                k                                      ·                          X                              i                ,                j                ,                k                                              +                      N                          i              ,              j              ,              k                                                          Equation        ⁢                                  ⁢                  (          1          )                    
Wherein, Ri,j,k denotes a received symbol transmitted by a kth sub-carrier and a jth band in a ith time period.
τi,j denotes a phase difference resulting from a sampling clock offset.
ψi,j denotes a carrier phase-shift.
H denotes a channel estimation value.
Ni,j,k denotes a noise signal in the channel.
By equation (1), it is known that the conventional receiver requires the consumption of a great amount of resources due to the complicated computations during the above-mentioned computation processes.